Ultrasensitive electrochemical microcystin-LR immunosensor using gold nanoparticle functional polypyrrole microsphere catalyzed silver deposition for signal amplification

Abstract

This work designed an ultrasensitive electrochemical immunosensor for microcystin-LR (MC-LR) detection using gold nanoparticle functional polypyrrole microsphere (AuNP/PPyMS) as a novel signal tag to induce silver enhancement for signal amplification. The dispersed polypyrrole microsphere (PPyMS) synthesized with a chemical oxidative polymerization was used to load AuNP for labeling signal antibodies, which enhanced the detection signal due to large surface area. The proposed MC-LR immunosensor was constructed by coating a polyethylene glycol film on a carbon nanotubes modified electrode and then immobilizing MC-LR antigen on the film. With a competitive immunoassay format, coated MC-LR competed for MC-LR antibody with added target MC-LR to form antibody-antigen immunocomplex. Subsequently, the immunocomplex reacted with AuNP/PPyMS labeled signal antibodies. The MC-LR immunoreaction monitoring was achieved by the electrochemical stripping signal of the deposited silver catalyzed by AuNP/PPyMS. AuNP/PPyMS-mediated silver enhancement along with carbon nanotubes-promoted electron transfer led to high detection sensitivity of MC-LR. Under optimal conditions, the MC-LR immunoassay had a wide linear range of 0.25ngL−1 to 50μgL−1, low detection limit of 0.1ng L−1, and good precision, reproducibility and stability. The designed amplification strategy has potential application in the ultrasensitive electrochemical detection of other algae toxins.